Abstract

We have investigated ultrafast optical responses of undoped GaAs/n-type GaAs (i-GaAs/n-GaAs) epitaxial structures at room temperature using a reflection-type pump-probe technique. The built-in electric field in the i-GaAs layer is controlled by its thickness. It is found that the decay time of a photoexcitation-induced reflectivity change in a sub-picosecond range decreases with an increase in the built-in electric field strength. The observed optical response is related to the transport process of photogenerated carriers from the i-GaAs layer to the n-GaAs layer. The shortest response time about 60 fs demonstrates that the i-GaAs/n-GaAs structure is useful for ultrafast optical applications.

Received 07 March 2012Accepted 04 May 2012Published online 22 May 2012

Acknowledgments:

This work was partially supported by a Grant-in-Aid for Young Scientists B (No. 22740203) from the JSPS, and by the Kansai Research Foundation for technology promotion. The author, H.T., acknowledges a Grant-in-Aid for Young Scientists B (No. 22760010) from the JSPS. The author, M. N., is thankful to Grant-in-Aid for Challenging Exploratory Research (No. 24656018) from the JSPS.